The health of the tires of a vehicle generally has a direct impact on the safety and efficiency of such vehicle. For example, it is known that driving with under-inflated tires may result in poor fuel economy, increased tire wear, and hazardous condition.
There are known devices that monitor some of the tire properties that affect the health of the tire. For example, a tire-pressure monitoring system (TPMS) is an electronic device that monitors the air pressure of the tire. Typically, the driver of the vehicle is alerted when the air pressure of one of the tires is low.
Some TPMS, known as indirect TPMS, operate by detecting differences between the rotational speeds between the wheels of the vehicle. The theory of operation is based on the assumption that under-inflated tires have a lower diameter, and therefore, rotate faster than a fully inflated tire. Other TMPS, known as direct TPMS, measure the air pressure directly on each tire.
Some direct TPMS are inside the tire and use a microelectromechanical system (MEM) to measure the pressure inside the tire. For example, FIG. 1 shows TMPS 104 mounted on rim 102. A tire (not shown) is disposed around rim 102. TPMS 104 is attached to rim 102 by being screwed with nut 106. Such direct TPMS transmit the sensed information wirelessly to a receiver in the vehicle.